Method of making molded articles

Abstract

In a method of making molded articles, such as particleboard from mixtures of wood chips or like particles, bonding agents and reaction accelerators, initially the particles are divided into two portions A and B. Portion A is wetted with bonding agents and portion B is wetted with reaction accelerators. The two portions A and B are maintained separate until they are mixed loosely layered together and introduced randomly into a mold forming a mat. Within the mold, the mat formed by the particles of portions A and B are pressed together and the pressing action triggers the reaction hardening. Prior to the pressing step, the mutual contact of the particles in the mat of portions A and B causes only limited hardening bridges.

I claim: 
     
       1. In a method of molding particleboard or fiberboard from wood and plant matter particles and mineral fibers comprising: (a) blending said particles with an organic bonding agent, a polycondensation hardening agent and a reaction accelerator for said hardening agent,   (b) placing a mat layer of said mixture within a heated pressing means,   (c) pressing said mat to bond the particles into said board form, the improvement comprising:   (d) prior to step (a) separating the particulate material into two portions A and B,   (e) wetting the surface of the portion A particles only with the bonding agent,   (f) wetting the surface of the portion B particles only with the reaction accelerator,   (g) introducing the particles of the portion A and the portion B separately and in a random manner into a mold forming a loosely layered mat, and   (h) compressing the loosely layered mat formed of the portions A and B within the mold to intimately associate the materials and thereby initiate the reaction of the accelerator, and compact and bond the particles into a molded board.   
     
     
       2. Method, as set forth in claim 1, wherein the particles of the portion A being in the range of 30-70% of the material being molded and the particles of the portion B being in the range of 70-30% of the material being molded. 
     
     
       3. Method, as set forth in claim 1, including heating the particles of portion A and portion B at least during the introduction of the particles of portion A and portion B into the mold. 
     
     
       4. Method, as set forth in claim 1, including using wood chips for portion A and fibers for portion B. 
     
     
       5. Method, as set forth in claim 1, including introducing a fiber into the mold along with the particles of portion A and portion B with the fibers serving as a carrier for the accelerator. 
     
     
       6. In a method for molding particleboard or fiberboard from wood and plant material particles and mineral fibers comprising (a) blending said particles with an organic bonding agent, a polycondensation hardening agent and a reaction accelerator for said hardening agent,   (b) placing a mat layer of said mixture within a heated pressing means,   (c) pressing said mat to bond the particles into said board form, the improvement comprising:   (d) prior to step (a) separating the particulate material into two portions A and B forming portion A of 100 kg of chopped wood chips having a residual moisture of 4% with 16 kg of a 50% hydrous solution urea resin, forming the portion B by mixing 20 kg of fibers with a 5-7% residual moisture with 0.8 kg of a 20% hydrous solution of ammonium chloride acting as an accelerator, introducing the particles of portion A into a first scattering device, introducing the particles of portion B into a second scattering device, introducing the particles from the first scattering device and the second scattering device in a random manner into the pressing means in the form of a loosely layered mat, compressing the loosely layered mat formed of the portions A and B within the pressing means to intimately associate the materials and thereby initiate the reaction of the accelerator, and compact and bond the particles into a molded board.   
     
     
       7. Method, as set forth in claim 6, introducing heat to the particles of portion A and to the fibers of portion B as the particles and fibers are being placed into the pressing means. 
     
     
       8. Method, as set forth in claim 6, including introducing heat only to one of the particles of portion A and of the particles of portion B as the particles in the portion to be heated are placed in the pressing means. 
     
     
       9. Method, as set forth in claim 6 or 7, including the step of maintaining the mold surfaces at a temperature for preventing the transfer of heat out of the particles of portion A and portion B heated at least during the introduction of the particles into the mold. 
     
     
       10. Method, as set forth in claim 6 or 7, including introducing glass fibers to the mold along with the particles of portion A and portion B for reinforcing the molded article to be formed.